Australian investigators have announced that the underwater search for the missing Malaysian passenger jet will shift to an area of the Indian Ocean hundreds of kilometers south of the first suspected crash site.

Martin Dolan, chief commissioner of the Australian Transport Safety Bureau, said on Friday that an announcement would be made next week on where a 60,000-sq-km search of the ocean floor would be focused on.

"All the trends of this analysis will move the search area south of where it was," Dolan said. "Just how much south is something that we're still working on."

He said the probable crash site would be hundreds of kilometers south of where a remote-controlled underwater drone scoured 850-sq-km of seabed, in the first fruitless search that ended last month.

That search area was defined by acoustic signals suspected to have come from the missing plane's black boxes, which promised to be the best clue to finding Malaysia Airlines Flight 370.

But those signals are now widely thought to have come from some other source.

The new search area will not be based on new data, but on refined analysis of existing satellite information from the doomed Boeing 777, after it veered off course during a flight from Kuala Lumpur to Beijing on March 8.

Vast expanse

The search area is in the vast expanse of ocean that was thoroughly swept for floating debris by search aircraft in the weeks after the plane disappeared with 239 passengers and crew aboard. No trace of plane has been found.

Dolan said the analysis of search data yielded several interpretations.

"Specialists have used several different methodologies and bringing all of that work together to get a consensus view is what we're finalizing at the moment," he said.

Private contractors are expected to start the new search far off the west Australian coast in August using powerful side-scan sonar equipment capable of probing ocean depths of 7-km. The job is expected to take up to 12 months to complete.

Two survey ships are currently mapping uncharted expanses of seabed in the search zone before the sonar scanning starts.

Dolan said the new search area would not be as far southwest of the coastal city of Perth as the initial air search had focused, near the limit of planes' range and in storm-prone seas.